In this July 28 photo, NASA Administrator Bill Nelson views the Space Launch System for the Artemis 1 mission inside the Vehicle Assembly Building. Credit: NASA/Kim Shiflett
The earliest NASA’s first Space Launch System moon rocket could roll out from the Vehicle Assembly Building to its seaside launch complex in Florida is in late November, officials told Spaceflight Now, leaving little time to conduct a critical fueling test, roll the rocket back into the VAB for final closeouts, then return to the pad for liftoff before the end of the year.
Stacking and testing of the SLS heavy-lift rocket has taken longer than NASA’s best-case projections earlier this year. But that’s not unexpected for the first time teams have assembled the powerful new launch vehicle inside the VAB at NASA’s Kennedy Space Center.
“It’s gone well, in my opinion, for first-time operations,” said Cliff Lanham, senior vehicle operations manager for NASA’s exploration ground systems program, in a recent interview with Spaceflight Now. “Everything is new for us, but in general, things have gone well.”
Lanham said NASA, supported by ground systems contractor Jacobs, intentionally delayed stacking of some elements of the Space Launch System this summer to complete some “higher-priority” work in the critical path for the first unpiloted SLS test flight, which NASA calls Artemis 1.
The higher-priority tasks included an initial power up of the SLS core stage avionics, and loading of flight software into the rocket’s computer system. The work also involved checkouts of an environmental control system before power-up of the rocket.
NASA engineers have not discovered any major problems during the SLS testing, but key milestones leading up to the Artemis 1 launch have been steadily sliding to the right in NASA’s processing schedule.
Before NASA raised the Boeing-made SLS core stage onto its mobile launch platform inside High Bay 3 of the VAB in June, managers hoped to connect he Orion spacecraft for the Artemis 1 mission on top of the rocket in August. That’s now expected this fall.
The first rollout of the 322-foot-tall (98-meter) rocket from the VAB to launch pad 39B was scheduled no earlier than September. That’s now expected in late November, at the soonest, according to Lanham.
The schedule slips, while not significant amid the history of SLS program delays, have put a major crunch on NASA’s ambition to launch the Artemis 1 mission this year. The agency is evaluating Artemis 1 launch opportunities in the second half of December, multiple sources said, but that would require NASA to cut in half the time it originally allotted between the SLS fueling test and the actual launch date.
Earlier this month, NASA stacked a test article of the Orion Stage Adapter on top of the SLS in High Bay. The flight adapter will connect the Orion spacecraft with the SLS upper stage, and will also carry around a dozen CubeSats into deep space as rideshare payloads.
Then ground teams lifted a cylinder called the Mass Simulator for Orion on top of the rocket. That structure mimics the weight of the Lockheed Martin-built Orion spacecraft, allowing technicians to complete resonance measurements on the entire rocket stack, a milestone NASA calls modal testing.
The Mass Simulator for Orion, a structure meant to mimic the weight of NASA’s Orion spacecraft, was mounted on top of the SLS stack earlier this month at NASA’s Kennedy Space Center. Credit: NASA
With the mass simulator stacked, ground teams began a series of interface verification tests earlier this. Those will be followed by an Umbilical Release and Retract Test, in which engineers will verify the release system for the swing arms routing fluid and support connections between the mobile launch tower and the SLS rocket.
The swing arms will rotate or drop away from the rocket at liftoff.
Then teams will move into modal testing. Stingers, or shakers, will introduce vibrations to the rocket as it stands on its support posts at the base of the mobile launch platform. Sensors across the rocket and along the mobile launch tower, will measure the resonant response to the vibrations.
The rocket’s twin side-mounted solid-fueled boosters each stand on four vehicle support posts, with the vehicle’s weight holding it on the mobile platform — without the support of hold-down bolts — during stacking, rollout, and the countdown before liftoff.
Lanham said NASA’s ground systems team hopes to finish the modal testing in September.
So we would get into, you know, towards the end of August into early September timeframe, we would get into URL T followed by modal, and ideally finish up in the middle of September with modal testing.
That will be followed by removal of the Orion mass simulator and the Orion Stage Adapter test article. Those will be replaced by the flight-ready stage adapter and the real Orion spacecraft, which has been fueled with in-space maneuvering propellant and mated with its launch abort system at Kennedy.
Technicians are completing installation of ogive fairings over the top of the Orion spacecraft, providing the aerodynamic shield that will cover the capsule during launch.
After additional tests to verify the mechanical and electrical connections between the Orion spacecraft and the SLS rocket, NASA will be ready to roll the fully-assembled launcher to pad 39B atop one of the agency’s Apollo-era crawler transporters.
The rocket will spend about a week on the pad before NASA’s launch team runs through a simulated countdown, culminating in the loading of super-hold liquid hydrogen and liquid oxygen aboard the launch vehicle.
Assuming that test, known as a wet dress rehearsal, is a success, teams will drain the propellant, safe the rocket, and return the Space Launch System to the Vehicle Assembly Building for final closeouts.
The time-sensitive work inside the VAB after the wet dress rehearsal will include the installation of pyrotechnic ordnance for the rocket’s separation systems and range safety destruct mechanism, which would terminate the flight if the rocket flew off course after liftoff.
Then the rocket will roll back out to pad 39B for another week of preparations ahead of the first launch attempt.
During launch, the core stage’s Aerojet Rocketdyne RS-25 engines and twin solid rocket boosters will generate 8.8 million pounds of thrust. It can send about 59,500 pounds (27 metric tons) of payload to the moon, according to NASA.
The Artemis 1 mission will propel the Orion spacecraft on a mission to orbit the moon for several weeks, before the capsule returns to Earth for a splashdown in the Pacific Ocean. Artemis 1 will pave the way for the next SLS/Orion mission, Artemis 2, to carry a four-person crew around the moon in 2023.
Artemis missions later in the 2020s will land astronauts near the south pole of the moon using commercially-developed lunar landers. In April, NASA selected a variant of SpaceX’s Starship, a reusable heavy-lift rocket being developed with majority private funding, to land the first Artemis crew on the moon.
But NASA plans to use the government-owned Space Launch System rocket and Orion capsule for the round-trip flight between Earth and the vicinity of the moon, where astronauts will transfer into a lunar lander, such as the Starship, for descent to the surface.